Ink-jet printing method and an ink-jet printing head

ABSTRACT

A method of ink-jet printing is implemented by focusing a laser light beam on an ink disposed in capillaries of a head and producing shock pulses therein resulting in ejection of drops of said ink onto an information carrier. An ink-jet printing head has a light beam laser having devices for focusing and deflecting the light beam across the nozzles bases for carrying out ejection of ink drops therefrom according to a predetermined program.

FIELD OF INVENTION

This invention pertains to the office equipment, particularly toprinting devices. More particularly the invention relates to ink-jetprinting methods and printing heads for such printing intended for acontactless application of information on carriers of varioustypes—paper, film, ceramics, plastics, etc.

DESCRIPTION OF PRIOR ART

Known is an ink-jet printing method that comprise steps of positioningof an information carrier opposite to jet nozzles filled with a liquidexpendable printing material, and excitation of pressure pulses in thesenozzles for a dispensed supply of the printing material onto theinformation carrier (U.S. Pat. No. 4,410,359). In the known method, apressure pulse in nozzles is produced owing to a pulse heating of aliquid printing material resulting in producing a vapour in the heatingarea, rapid expansion of a liquid and ejection of its drop from anozzle.

A drawback of this method consists in that a source that provides athermal action effected on an ink is positioned immediately in eachnozzle and controlled externally, which makes realisation of this methoddifficult when there is great a number of nozzles.

For implementation of the known ink-jet printing method, various ink-jetprinting heads are used, e.g. such that are described in U.S. Pat. No.4,508,148, cl. 346/14OR. This patent describes an ink-jet printing headcomprising as many resistors for ink heating as there are nozzlestherein. Each resistor has a current supply arrangement connecting it toa power supply. For ejection of a drop from a nozzle, the supply circuitof corresponding resistor is closed. When a current pulse flows througha resistor, the latter is heated and heats the ink located in the areawhere such resistor is disposed to the vaporous state, whereby theliquid, while expanding, creates a shock pulse which ejects a dropthereof through a nozzle. Thereafter, when the liquid is cooled off, theprocess may be repeated.

A drawback of such heads is their structural complexity, for such headmust have as many resistors as there are nozzles positioned at a littlespacing and provided with a current supply system; and a lowreliability, as the mode of resistor multiple pulse heating to asufficiently high temperature determines their limited service life.

DISCLOSURE OF THE INVENTION

The basic purpose of the invention consists in providing such method anda head for ink-jet printing that will exclude positioning of a source ofshock pulses for ink drops ejection from head nozzles immediately in ahead, simplify the head structure and improve reliability and durabilityof its operation.

The set purpose is to be attained as follows: In an ink-jet printingmethod comprising steps of positioning an information carrier oppositeto jet nozzles filled with a liquid expendable printing material, andexcitation of pressure pulses in these nozzles for a dispensed supply ofthe printing material onto an information carrier, according to theinvention a quantum generator (laser) light beam is focused on theliquid printing material disposed on the nozzles so that shock pulsesare produced as the light beam is absorbed by this material.

In such method, a source of a shock action effected on an ink is locatedoutside the nozzles or cavities with an ink adjacent to them, whichallows to improve quality of printing owing to diminishing of thenozzles diameter and a spacing therebetween, and simplifies possibilityof realisation of said source when there is a great number of nozzles.

The set purpose is also attained through in that in an ink-jet printinghead comprising a number of nozzles in the form of capillary openingsfilled with a liquid expendable printing material, and means forproducing a pressure pulse in a capillary for a dispensed supply of thismaterial onto an information carrier, according to the invention themeans for producing a pressure pulse in a capillary is arranged in theform a light beam laser having a device for focusing said beam to a sizesmaller then the capillary diameter, and a device for deflecting thebeam across nozzle bases from the side that is opposite to aninformation carrier.

Such arrangement of an ink-jet printing head simplifies its design,because in the head nozzles there are no elements producing the actionof a shock action effected on a liquid, and a head itself has no systemfor supplying current to said elements; reliability of its operation isenhanced owing to simplification of the design and exclusion therefromof any parts operating in the sharp temperature drop mode.

The nozzle bases are preferably open and nozzles, over the bases levelupward, communicate with channels for procuring an expendable printingmaterial for them.

The nozzle bases are also preferably covered with a material which istransparent to a wavelength emitted by a laser.

Such arrangement of a head permits that a laser light beam will actefficiently on an ink disposed in a nozzle and produce shock pulsestherein to eject drops thereof onto an information carrier.

BRIEF DESCRIPTION OF DRAWINGS

Hereinafter the invention will be explained by its particular but notlimiting embodiments, and accompanied drawings wherein:

FIG. 1 illustrates the proposed method of the ink-jet printing,

FIG. 2 general view of the proposed ink-jet printing head for embodyingan ink-jet printing method with open nozzle bases,

FIG. 3 ditto, as FIG. 2 with closed nozzle bases,

FIG. 4 section along II—II line of FIG. 2.

BEST MODES FOR CARRYING OUT THE INVENTION

The proposed method of an ink-jet printing is implemented as follows:

An information carrier C (FIG. 1) is positioned opposite to nozzles Bfilled with a liquid expendable printing material. Thereafter a lightbeam emitted from laser E is focused on the liquid printing material. Inaccordance with the discovery named as “Lighthydraulic Effect” (diplomaN 65 BI N 19, 1969), when a laser light beam is absorbed within aliquid, a shock pulse (wave) is produced. Energy release is ensured,when the ‘Lighthydraulic Effect’ takes place, due to a powerful shortlight pulse.

With this effect a shock pulse is created within nozzle B itself whichis filled with a liquid printing material, whereby a drop of the liquidis ejected from the nozzle and hits the information carrier.

From the above-cited description of the proposed method it is obviousthat a source that effects a shock action on an ink is located outsidethe nozzles or cavities with the ink adjacent to them, which allows oneto improve quality of printing owing to the provided possibility todiminish the drops diameter and increase density of their positioning onan information carrier.

For realisation of the proposed ink-jet printing method, it is necessarythat a laser light beam sweep will be provided across the bases fonozzles filled with an ink. This is done by an ink-jet printing headshown in FIG.2

The proposed ink-jet printing head comprises a number of nozzles 1 inthe form of capillary openings filled with a liquid expendable printingmaterial supplied into nozzles form channel 2 (FIG.4). Informationcarrier 3 is positioned perpendicularly to axes of nozzles 1. Oppositeends of nozzles, their bases face laser 4 of light beam 5 having devicesfor focusing 6 of the beam and deflection 7 thereof across bases ofnozzles 1. Nozzles 1 bases are arranged to be either open, or covered bymaterial 8 (FIG. 3) that is transparent to a wavelength emitted by laser4.

The proposed ink-jet printing head operates as follows:

Beam 5 of laser 4 according to a predetermined program is focused usingdevice 6 and directed using device 7 for its deflection onto a liquiddisposed in a given nozzle 1. As light beam 5 is absorbed within theliquid, the lighthydraulic effect is produced whereby in the liquiddisposed in a capillary a shock pulse is produced, due to action ofwhich pulse a drop of the ink is ejected form nozzle 1 and hitsinformation carrier 3. Then the action effected beam 5 on the givennozzle 1 is terminated such that the ink for compensation of the ejecteddrop is supplied to the nozzle form channel 2. By deflecting beam 5 oflaser 4 across bases fo nozzles 1 according to a predetermined program,as set of dots representing a text or an image on information carrier 3can be obtained.

INDUSTRIAL APPLICABILITY

An ink-jet printing head is intended for visual high resolutionrepresentation of a textural or graphical information on any type of acarrier.

What is claimed is:
 1. A method of ink-jet printing comprising the stepsof positioning an information carrier opposite to a jet nozzlecomprising a capillary extending from a base to a nozzle opening, saidcapillary filled with a liquid expendable printing material and imposinga pulse of laser light on the liquid printing material in the capillarysufficient to generate a hydraulic shock wave in the liquid printingmaterial and expel the liquid printing material from the nozzle to theinformation carrier.
 2. The method of ink-jet printing of claim 1 whichcomprises the step of refilling the capillary with the liquid printingmaterial and repeating the imposing said pulse of laser light on theliquid printing material.
 3. The method of ink-jet printing of claim 2in which the refilling and imposing steps are repeated a plurality oftimes.
 4. A method of ink-jet printing according to claim 3 in which thelaser light beam is focussed to a size smaller than a dimension of thecapillary transverse to the axis form the base to the opening.
 5. Anink-jet printing head comprising a plurality of nozzles each of whichcomprises a capillary extending from a base to a nozzle opening adaptedto be positioned opposite an information carrier, a laser adapted torelease pulses of a laser light beam, a focussor adapted to focus thelaser light beam to a size smaller than a capillary dimension transverseto the axis from a nozzle base to a nozzle opening and a deflectoradapted to deflect the laser light beam to the capillary at the nozzlebase.
 6. An ink-jet printing head as claimed in claim 5 in which thenozzle base comprises a cover through which the laser light beam cantravel.
 7. An ink-jet printing head as claimed in claim 6 comprising asupply of liquid expendable printing material for the capillary.
 8. Anink-jet printing head as claimed in claim 7 in which the supplycomprises a liquid printing material supply channel communicating withan aperture in the capillary.